unify timezone handling across task-decomp flow

nenrinyear · ikotome · commit 8f0126d9212b · 2026-02-22T10:44:49.000+09:00
diff --git a/backend/src/features/task-decompose/task-calendar.service.ts b/backend/src/features/task-decompose/task-calendar.service.ts
@@ -3,6 +3,7 @@ import type {
   TaskDecomposeRequest,
   TaskDecomposeResult,
 } from "./task-decompose.types";
+import { normalizeTaskTimezone } from "./task-timezone";
 import type {
   CalendarCreatedEvent,
   CalendarSyncResult,
@@ -296,7 +297,7 @@ export async function createCalendarEvents(
   input: CreateCalendarEventsInput,
 ): Promise<CalendarSyncResult> {
   const accessToken = await getGoogleAccessToken(env, input.userId);
-  const timezone = input.request.timezone ?? "UTC";
+  const timezone = normalizeTaskTimezone(input.request.timezone);
   const calendarId = PRIMARY_CALENDAR_ID;
   const overallTaskName = toOverallTaskName(
     input.request.task,
diff --git a/backend/src/features/task-decompose/task-decompose.service.ts b/backend/src/features/task-decompose/task-decompose.service.ts
@@ -3,13 +3,13 @@ import type {
   TaskDecomposeResult,
   TaskSubtask,
 } from "./task-decompose.types";
+import { normalizeTaskTimezone } from "./task-timezone";
 
 const AI_MODEL = "@cf/meta/llama-3.1-8b-instruct-fp8";
 const DEFAULT_MAX_STEPS = 6;
 const MIN_DURATION_MINUTES = 15;
 const MAX_DURATION_MINUTES = 240;
 const DEFAULT_INFERRED_DEADLINE_DAYS = 7;
-const DEFAULT_PLANNING_TIMEZONE = "Asia/Tokyo";
 
 function asStringArray(value: unknown): string[] {
   if (!Array.isArray(value)) {
@@ -76,14 +76,6 @@ function fallbackSummary(task: string): string {
   return `"${task}" を実行可能な単位へ分解した計画です。`;
 }
 
-function normalizeTimezone(timezone: string | undefined): string {
-  if (!timezone || timezone.trim().length === 0) {
-    return DEFAULT_PLANNING_TIMEZONE;
-  }
-
-  return timezone.trim();
-}
-
 function formatPromptDateInTimezone(date: Date, timezone: string): string {
   try {
     return new Intl.DateTimeFormat("en-CA", {
@@ -260,7 +252,7 @@ function normalizeResult(
 
 function createPrompt(payload: TaskDecomposeRequest): string {
   const maxSteps = payload.maxSteps ?? DEFAULT_MAX_STEPS;
-  const planningTimezone = normalizeTimezone(payload.timezone);
+  const planningTimezone = normalizeTaskTimezone(payload.timezone);
   const now = new Date();
 
   const deadlineGuidance = payload.deadline
diff --git a/backend/src/features/task-decompose/task-decompose.validation.ts b/backend/src/features/task-decompose/task-decompose.validation.ts
@@ -1,4 +1,5 @@
 import type { TaskDecomposeRequest } from "./task-decompose.types";
+import { normalizeTaskTimezone } from "./task-timezone";
 
 const MAX_STEPS_LIMIT = 12;
 
@@ -20,17 +21,12 @@ function parseDeadline(value: unknown): string | undefined {
   return parsed.toISOString();
 }
 
-function parseTimezone(value: unknown): string | undefined {
+function parseTimezone(value: unknown): string {
   if (typeof value !== "string") {
-    return undefined;
-  }
-
-  const trimmed = value.trim();
-  if (trimmed.length === 0) {
-    return undefined;
+    return normalizeTaskTimezone(undefined);
   }
 
-  return trimmed;
+  return normalizeTaskTimezone(value);
 }
 
 function parseMaxSteps(value: unknown): number | undefined {
diff --git a/backend/src/features/task-decompose/task-timezone.ts b/backend/src/features/task-decompose/task-timezone.ts
@@ -0,0 +1,18 @@
+const DEFAULT_TASK_TIMEZONE = "Asia/Tokyo";
+
+export function normalizeTaskTimezone(
+  value: string | null | undefined,
+): string {
+  if (!value || value.trim().length === 0) {
+    return DEFAULT_TASK_TIMEZONE;
+  }
+
+  const candidate = value.trim();
+  try {
+    return new Intl.DateTimeFormat("en-US", {
+      timeZone: candidate,
+    }).resolvedOptions().timeZone;
+  } catch {
+    return DEFAULT_TASK_TIMEZONE;
+  }
+}
diff --git a/frontend/src/app/task-decomp/components/task-decomp-steps.tsx b/frontend/src/app/task-decomp/components/task-decomp-steps.tsx
@@ -58,6 +58,7 @@ type ResultStepProps = {
   phase: RunPhase;
   statusLabel: string;
   record: WorkflowRecord | null;
+  userTimezone: string;
   displayErrorMessage: string | null;
   onStartNewTask: () => void;
 };
@@ -335,11 +336,13 @@ export function ResultStep({
   phase,
   statusLabel,
   record,
+  userTimezone,
   displayErrorMessage,
   onStartNewTask,
 }: ResultStepProps) {
   const breakdown = record?.llmOutput;
   const calendarResult = record?.calendarOutput;
+  const displayTimezone = record?.timezone ?? userTimezone;
 
   return (
     <Stack gap={5}>
@@ -381,8 +384,7 @@ export function ResultStep({
                       </Text>
                       <HStack gap={2} flexWrap="wrap">
                         <Badge colorPalette="blue" variant="subtle">
-                          期限:{" "}
-                          {formatDateTime(subtask.dueAt, record?.timezone)}
+                          期限: {formatDateTime(subtask.dueAt, displayTimezone)}
                         </Badge>
                         <Badge colorPalette="teal" variant="subtle">
                           {subtask.durationMinutes} 分
@@ -418,12 +420,12 @@ export function ResultStep({
                           <Text fontSize="sm" color="fg.muted">
                             {formatDateTime(
                               eventItem.startAt,
-                              calendarResult.timezone,
+                              calendarResult.timezone ?? displayTimezone,
                             )}{" "}
                             -{" "}
                             {formatDateTime(
                               eventItem.endAt,
-                              calendarResult.timezone,
+                              calendarResult.timezone ?? displayTimezone,
                             )}
                           </Text>
                         </Stack>
diff --git a/frontend/src/app/task-decomp/helpers.ts b/frontend/src/app/task-decomp/helpers.ts
@@ -89,14 +89,48 @@ export function formatDateTime(
     return value;
   }
 
-  return parsed.toLocaleString("ja-JP", {
-    timeZone: timezone ?? DEFAULT_USER_TIMEZONE,
-    year: "numeric",
-    month: "2-digit",
-    day: "2-digit",
-    hour: "2-digit",
-    minute: "2-digit",
-  });
+  const safeTimezone = normalizeTimezone(timezone);
+  try {
+    return parsed.toLocaleString("ja-JP", {
+      timeZone: safeTimezone,
+      year: "numeric",
+      month: "2-digit",
+      day: "2-digit",
+      hour: "2-digit",
+      minute: "2-digit",
+    });
+  } catch {
+    return parsed.toLocaleString("ja-JP", {
+      year: "numeric",
+      month: "2-digit",
+      day: "2-digit",
+      hour: "2-digit",
+      minute: "2-digit",
+    });
+  }
+}
+
+export function normalizeTimezone(timezone: string | null | undefined): string {
+  if (!timezone || timezone.trim().length === 0) {
+    return DEFAULT_USER_TIMEZONE;
+  }
+
+  const candidate = timezone.trim();
+  try {
+    return new Intl.DateTimeFormat("en-US", {
+      timeZone: candidate,
+    }).resolvedOptions().timeZone;
+  } catch {
+    return DEFAULT_USER_TIMEZONE;
+  }
+}
+
+export function detectBrowserTimezone(): string {
+  if (typeof window === "undefined") {
+    return DEFAULT_USER_TIMEZONE;
+  }
+
+  return normalizeTimezone(Intl.DateTimeFormat().resolvedOptions().timeZone);
 }
 
 export function toStatusLabel(
diff --git a/frontend/src/app/task-decomp/page.tsx b/frontend/src/app/task-decomp/page.tsx
@@ -37,8 +37,9 @@ import {
   ResultStep,
   RunningStep,
 } from "./components/task-decomp-steps";
-import { DEFAULT_USER_TIMEZONE, STEP_ITEMS } from "./constants";
+import { STEP_ITEMS } from "./constants";
 import {
+  detectBrowserTimezone,
   formatDateTime,
   needsCalendarReauth,
   toDeadlineIso,
@@ -105,6 +106,7 @@ export default function TaskDecompPage() {
   const loadedDraftUserIdRef = useRef<string | null>(null);
 
   const signedInUser = useMemo(() => session?.user ?? null, [session]);
+  const userTimezone = useMemo(() => detectBrowserTimezone(), []);
   const statusLabel = useMemo(
     () => toStatusLabel(phase, workflowStatus, record),
     [phase, workflowStatus, record],
@@ -371,8 +373,7 @@ export default function TaskDecompPage() {
     const safeMaxSteps = Number.isFinite(parsedMaxSteps)
       ? Math.min(Math.max(Math.trunc(parsedMaxSteps), 1), 12)
       : 6;
-    const timezone =
-      Intl.DateTimeFormat().resolvedOptions().timeZone ?? DEFAULT_USER_TIMEZONE;
+    const timezone = userTimezone;
 
     setPhase("starting");
     setErrorMessage(null);
@@ -539,6 +540,7 @@ export default function TaskDecompPage() {
         phase={phase}
         statusLabel={statusLabel}
         record={record}
+        userTimezone={userTimezone}
         displayErrorMessage={displayErrorMessage}
         onStartNewTask={handleStartNewTask}
       />
@@ -695,7 +697,7 @@ export default function TaskDecompPage() {
                                   <Text fontSize="xs" color="fg.muted">
                                     {formatDateTime(
                                       item.createdAt,
-                                      item.timezone,
+                                      item.timezone ?? userTimezone,
                                     )}{" "}
                                     / {toStatusLabelFromRecord(item.status)}
                                   </Text>
